Wertz P W, Swartzendruber D C, Abraham W, Madison K C, Downing D T
Department of Dermatology, Marshall Dermatology Research Laboratories, University of Iowa College of Medicine, Iowa City 52242.
Arch Dermatol. 1987 Oct;123(10):1381-4.
The intercellular spaces of the stratum corneum contain multilamellar lipid sheets derived from the extruded contents of lamellar granules. In the absence of linoleic acid, lamellar granules appear empty, and only fragmentary extracellular sheets are found. This defective differentiation is attributable to substitution of oleate for linoleate in O-acylsphingolipids. Normally, linoleate is ester-linked to 30- to 34-carbon omega-hydroxyacids, which, in turn, are amide-linked to sphingosine. Acylglucosylceramides, bearing a beta-D-glucosyl moiety on the sphingosine, may provide the driving force for lamellar granule assembly. The omega-hydroxyacyl chains are long enough to span a lipid bilayer, while the linoleate inserts into an adjacent bilayer. This interaction could promote assembly of lamellar granules. It has also been proposed that acylceramides may stabilize the extracellular sheets by a similar mechanism. In addition, the horny cell has been found to possess a covalently bound lipid envelope consisting principally of omega-hydroxyacylsphingosines derived from O-acylsphingolipids.
角质层的细胞间隙含有源自板层颗粒挤出内容物的多层脂质片层。在缺乏亚油酸的情况下，板层颗粒看起来是空的，仅发现碎片状的细胞外片层。这种分化缺陷归因于在O-酰基鞘脂中亚油酸被油酸替代。正常情况下，亚油酸通过酯键与30至34个碳原子的ω-羟基酸相连，而这些ω-羟基酸又通过酰胺键与鞘氨醇相连。在鞘氨醇上带有β-D-葡萄糖基部分的酰基葡萄糖神经酰胺可能为板层颗粒的组装提供驱动力。ω-羟基酰基链足够长以跨越一个脂质双层，而亚油酸插入相邻的双层中。这种相互作用可能促进板层颗粒的组装。也有人提出酰基神经酰胺可能通过类似机制稳定细胞外片层。此外，已发现角质形成细胞拥有一个共价结合的脂质包膜，其主要由源自O-酰基鞘脂的ω-羟基酰基鞘氨醇组成。
